Toxigenic bacteria and sudden infant death syndrome (SIDS): nasopharyngeal flora during the first year of life

Abstract

Many developmental and environmental risk factors for sudden infant death syndrome (SIDS) are similar to those for susceptibility to respiratory tract infection, and toxigenic bacteria have been implicated in some SIDS cases. We assessed nasopharyngeal flora of healthy infants in relation to risk factors to determine which species best lit the mathematical model proposed for the common bacterial toxin hypothesis and if these findings complemented results obtained from SIDS cases which occurred during the period of the survey. Longitudinal studies were carried out between April 1993 and March 1996 on 253 healthy infants and their mothers. 150 from a multiply deprived area, 103 from an affluent area. Concurrent SIDS infants (37) were screened for nasopharyngeal flora. Among healthy infants < or = 3 months of age, the predominant isolate was Staphylococcus aureus 57% compared with 86% for SIDS infants in that age range (P< 0.02). There were significant associations between isolation of different species from both mother and baby but no association between isolation of any species with: area of residence: parental smoking habits; breast or bottle feeding; symptoms of viral infection: seasonality. We conclude that S. aureus fits the mathematical model for SIDS. Both staphylococci and/or their toxins were identified in a significant proportion of SIDS cases. Isolation of staphylococci from healthy infants was associated with the 2-4-month age range, a risk factor consistently found in all epidemiological studies of SIDS. This might reflect the developmental stage in which 80-90% of infants express the Lewis(a) antigen which we have shown to be one of the receptors for S. aureus.

Sudden Infant Death Syndrome: A Review of the Literature

“…This calls for more intense and targeted education toward these high-risk groups. Finally, SIDS has been correlated with having a recent infection [65,66], with decreased arousability as the suspected link. This has been supported by polysomnographic studies demonstrating higher arousability thresholds [67], and biochemical research showing increased levels of somnogenic substances [13], in infants following an illness, typically an upper respiratory infection.…”

Postmortem investigation of sudden unexpected death in infancy: current issues and autopsy protocol

“…aureus is significantly more common in SIDS infants 3 months old or younger than in agematched healthy controls. 75 Furthermore, it has been demonstrated that prone sleeping in the presence of an upper respiratory tract infection is associated with significantly increased bacterial carriage, including increased colonization by staphylococci, 76 and a recent study reported significantly more isolates of so-called 'group 2 pathogens' (recognized pathogens known to cause bacteraemia without an obvious focus of infection) in unexplained SUDI cases compared to SUDI deaths due to known non-infective causes, such as accidents or congenital heart Histological causes of death in explained sudden unexpected death in infancy (SUDI). a The commonest histological diagnosis is pneumonia.…”

Infectious causes of sudden infant death syndrome

“…Autopsies on cases of SIDS showed increased isolation of staphylococci and Gram-negative bacilli compared with matched healthy controls [28]. Some studies showed that Staphylococcal toxins and endotoxins were present in SIDS tissues but antibodies to endotoxins were low, leading to the common bacterial ''toxin hypothesis'' [29].…”

“…] TOXIGENIC BACTERIA AND SIDS Studies suggest that in some cases of SIDS nasopharyngeal bacterial toxins may trigger events that may lead to an infant's death. One large observational study by Blackwell et al [28] attempted to explore which species fitted with the bacterial toxin hypothesis by assessing the nasopharyngeal flora of healthy infants in relation to risk factors. That study showed that in healthy infants 3 months of age, Staphylococcus aureus (S. aureus) was isolated in 57% compared with 86% for SIDS infants in that age range (P<0.02).…”

“…That study showed that in healthy infants 3 months of age, Staphylococcus aureus (S. aureus) was isolated in 57% compared with 86% for SIDS infants in that age range (P<0.02). S. aureus fitted with the mathematical model for SIDS, and staphylococci with their toxins were identified in a relatively significant proportion of SIDS cases [28].…”